Slitherine

I'm wondering if it is possible to have some part of your units under AI control? It seems this can be done just by adding the same faction multiple times (see screenshot) but I'm wondering if this is intended to work, because adding the same nation third time seems to make the mission stuck at load screen. So before I do this I would like to know will there be some kind of horrible bugs with this method.

I know I could add duplicate factions by modding but I would like to stay with the vanilla game.

Based on my experience, if you add the same faction for the third time, it will always cause the game to become stuck. Two times - it will be ok, but You must mark both as one team.

Back in the day the plan was to be able to add multiple instances of the same faction and use different icons.
Never implemented.
It would remove the need to create mods to handle this.

Ok, thanks for the answers!

As others said, having two times the same faction is ok. I like to do it to split big armies and relieve some of the Command&Control weight off the player's shoulders. I also think it's more wargame-like to have the player not be able to micromanage the entire faction from time to time, and giving part of it to the AI simulates well how less-skilled colleagues would frustrate a good general's plans, forcing him to adapt and, on occasion, "rescue" said colleague.